A. Field of the Invention
The present invention relates to synthetic polymer fibers or filaments having denier fluctuations or variations of random size in the direction of the axis thereof, yarns made therefrom, and a method of preparing same.
B. Description of the Prior Art
Man-made fibers are generally produced by spinning and drawing. In most instances, the fibers produced by this procedure are substantially uniform in thickness.
In certain applications, it is important that yarns contain filaments having a variable denier. For instance, such yarns are useful in providing the means of producing variable texture and dyeing effects in fabrics made therefrom. Thus, mottled or other novelty effects can be produced owing to the varying rates and extents to which dyestuff is taken up by the portions of different denier. Fabrics containing such yarns have an attractive appearance, i.e., a "busy" looking fabric, and a pleasing hand-feel.
The term "fiber" as used herein includes fibers of extreme or indefinite length (i.e., filaments) and fibers of short length (i.e., staple). The term "yarn" as used herein means a continuous strand of fibers.
The term "fabric" as used herein includes a textile structure composed of mechanically interlocked fibers or filaments. The structure can be nonwoven, woven, or knitted.
The term "multifilament yarn" as used herein means a multifilament yarn comprising a plurality of individual filaments or modification of said multifilament yarn.
A number of procedures have been proposed in the past for producing filaments having a variable denier. One such proposal involves a controlled irregularity in the feed rate of the filament-forming mass to the spinning nozzles. The pressure variations resulting from these controlled changes of the feed rate cause corresponding changes in the thickness of the resulting filament. Another proposal involves drawing off the filaments from the spinning nozzle at a variable or changing velocity. Still another procedure for producing filament-containing yarn having a variable denier involves drawing the filaments around a hot pin at lower than normal draw ratios and temperatures.
On particularly undesirable feature associated with many of these proposals is that the larger denier portions, sometimes referred to as "slubs", of the filaments have a short length. In order for a fabric containing the variable denier filaments to have a pleasing "linen-like" appearance, and/or to have attractive novelty effects, it is desirable that the fabric contain filaments having slubs of longer length.
The present invention provides filaments having longer slubs, even up to 8 times the length of previous variable denier filaments, which find particular application in fabrics where variable texture and dyeing effects are desirable.